Evaporator construction for heat exchange systems



Feb. 16, 1954 MALKOFF 2,669,099

EVAPORATOR CONSTRUCTION FOR HEAT EXCHANGE SYSTEMS Filed Dec. 29, 1950 5 Sheets-Sheet 1 IN V EN TOR.

H. MALKOFF Feb. 16, 1954 EVAPORATOR CONSTRUCTION FOR HEAT EXCHANGE SYSTEMS Filed D60. 29, 1950 I5 Sheets-Sheet 2 k w M INVENTOR.

1954 MALKOFF 2,669,099

EVAPORATOR CONSTRUCTION FOR HEAT EXCHANGE SYSTEMS 3 Sheets-Sheet 5 Feb. 16,

Filed Dec. 29, 1950 INVENTOR.

Patented Feb. 16, 1954 EVAPORATOR CONSTRUCTION FOR HEAT EXCHANGE SYSTEMS Hyman Malkoflf, Trenton, N. J., assignor to Kramer Trenton Company, Trenton, N. J., a corporation of New Jersey Application December 29, 1950, Serial No. 203,400

This invention relates to heat exchange systems or apparatus and, more particularly, to

the construction and arrangement of the evaporator portion thereof; and has for an object to provide a construction in which provision is made for evaporating refrigerant liquid that has failed to be evaporated during its passage through the evaporator due principally to lack of correct relationship between the amount of liquid refrigerant supplied to the individual conduits or passes of the evaporator and the heat load imposed thereupon by the air circulating means of the system.

Another object is to provide such a construction which embodies an auxiliary or after evaporator which receives refrigerant moving from the main evaporator and serves to evaporate the liquid portion of the same prior to the entry of the refrigerant into the suction line leading to the compressor of the system."

Another object is to provide such a construction in which the auxiliary or after evaporator is positioned in the path of the current generated by the air circulating means of the system and approaching the main evaporator.

Another object is to provide such a construction in which the auxiliary or after evaporator is positioned between the main evaporator and the air circulating means of the system.

Another object is to provide such a construction in which the after evaporator is positioned within the main evaporator.

Another object is to provide such a construction in which at least part of the conduits or passes of the main evaporator are soformed as to assist in causing the refrigerant to traverse the individual conduits or passes of the evaporator in accordance with the heat load demands imposed upon the said conduits or passes by the air circulating means of the system, with the result of increasing the effectiveness of the main evaporator and reducing the percentage of refrigerant that moves therefrom in liquid form.

Another object is to provide such a construction in which the refrigerant supply conduit or line leading from the condenser and receiver, if a receiver is included in the system, passes in heat exchange relationship with a portion of the suction conduit or line leading to the compressor, before the said supply conduit or line reaches the expansion valve of the system, for the purpose of providing heat to the said suction line and evaporating that portion, if any, of the refrigerant therein which may not have been thoroughly evaporated by the main and auxiliary or after evaporator.

6 Claims. (Cl. 62-126) A further object consists in providing certain improvements in the form, construction and arrangement of the several parts whereby the above named and other objects inherent in the invention may be effectively attained.

Practical embodiments of the invention are represented in the accompanying drawings in which:

Fig. 1 represents, in part diagrammatically, a side elevation of a heat exchange system designed for refrigeration, and showing the auxiliary or after evaporator positioned between the air circulating fan and the main evaporator, as well as the formation of the conduits or passes of the main evaporator which assists in causing the refrigerant to traverse the individual conduits or passes of the evaporator in accordance with the heat load demands imposed thereupon;

Fig.2 represents a similar view of a modified form of the invention in which a portion of the refrigerant supply'conduit or line is arranged in heat exchange relationship with a portion of the suction conduit or line; I

Fig; 3 represents a vertical section, partly in elevation, taken on the line III-III of Fig. 1, looking in'the direction of the arrows; and

Fig. 4 represents an end elevation of a second modified form of the invention in which the auxiliary or after evaporator is positioned within the main evaporator.

' The evaporators of heat exchange systems such, for instahceas refrigeration apparatus, frequently comprise a plurality of tubular conduits or passes which are traversed by the refrigerant coming from the expansion valve of the system mainly in liquid form and which, in performing their chilling or freezing function, vaporize or evaporate a large portion of the refrigerant coursing therethrough. The outer surface of the said conduits or passes of the evaporator are subjected to an air current flowing therethrough from one side to the other which is commonly generated by a fan or blower positioned at one side of the evaporator, or by suction means positioned at the opposite side; and this air current necessarily imposes a greater heat load upon the conduits or passes of the evaporator that are nearer to the side of the evaporator towards which the air current moves than those conduits or passes which are more distant therefrom, because the air current is progressively chilled as it flows through the evaporator. Consequently, the different conduits or passes of the evaporator do not render equal service in their chilling or freezing function because a greater percentage of the liquid refrigerant is evaporated in some of the conduits or passes than in others owing to the above mentioned variation in heat load imposed thereupon by the air current. This reduces the efliciency of the evaporator as a whole, and an effort has been made to counteract this condition by supplying the refrigerant .coming from the expansion valve in unequal amounts to the several conduits or passes of the evaporator so that a greater amount of the refrigerant is supplied to the conduits or passes in accordance with their proximity to the side of the evaporator towards which the air current flows, with the object ofattaining that highly desirable practical-condition in which. the inner surface of each conduit or.,passis constantly wet with liquid refrigerant while the. refrigerant discharged therefrom in vapor form and at a slightly superhe'ated'temperature, for instance, of five to eight degrees Fahrenheit.

The present invention is designed and calculatedfurther to advance this. aspect .inithe field of heat exchange. systems by promoting .theefliciency of the. evaporator of the system and insuring the useful evaporation of anyrefrigerant which may be emitted therefrom inliquid form;

thus not only heightening the valueof thesystemas a whole with respect to its refrigerating function, but also preventing the return of liq- .uid refrigerant to the. compressor through the suction line.

Referring now to the form of the. invention shown in Fig. 1, the compressor of the system is denoted by I and its discharge is connected by .a conduit .2 with a unit .3 which may consist of a condenser and receiver or. of a condenser only. A. refrigerant supply line, 4 connects the outlet of. the unit. 3. with. the usuai expansion valve 5 which, in turn, communicates zbyxa conduit. B with. the .inlet 7 of. the .mainevaporator that .isidenoted generally-by 'I. andzthe outlet of. which is. connected, in: a manner, which will hereinafter he described, to the suction conduit or line 8, which communicates with .theinlet of the..com- 'pressor. .I. The action of the expansion valve 5 is controlled in the usual way through a capillary tube .9 that is connected with "a feeler. :bulb III which is suitably clamped or otherwise fixed to the suction conduit 8. An aircirculating fan II driven by an electric. motor I2, that. is

connected in any appropriate way withalazsouree of current (not shown) is mounted adjacent the evaporator I :for the. purpose of driving an air stream therethrough, as indicated by the'zarrow. As the compressor, condenser (with zonwithout receiver), expansion valve, Ifeeler :bulb. control therefor, and fan. with its motor may .beof any \well known or approved form, and asth'eir particular construction and arrangement "constitute no. part of the present invention, -it is deemedunnecessary further to illustrate'or describe the :same.

evaporator is fitted' with four distributors, I I,

1 8', I 9, 20, that communicate with the inlet ends of the conduits or passes I3, I4, #5, I5, respec- 'tively; while theoutlet ends of the said conduits or passes are connected as indicated at -2'I, 22,

23; 24, with an outlet manifold '25 that is disposed transversely of the said conduits '01" passes.

It will be observed that, as the inlet c'onduitfi running from the expansion valve to the main evaporator supplies the four conduits or passes of the evaporator, the distributors I'I, I8, I9, are of smaller cross sectional size than the conduit 6; and, conversely, as the outlet manifold receives the refrigerant from all four conduits-or passes .of the-xevaporator, it is substantially larger in cross section than the individual passes of the evaporator.

For the purpose of supplying the incoming liquid refrigerant to the passes I3, I4, I5, I6, of'itheymain evaporator I, in accordance with the needs of the individual passes, a criss-cross formationnf thesaid passes is provided at about "thencenter of thexmain evaporator, the arrangement-:beingrsuch ":that conduit or pass I5 is connected by a cross-over 26 with conduit I3. As pass I'6 isfurthestfrom the side of the evaporator towardsswhich the air current from fan I I flows, it is subjected to the lightest heat load of all the passes; while pass I3, being. :nearest tothe side of the evaporator towards, which .theair stream moves, is. subjectedv to the heaviest heat, load.

Consequently, the;.-liquid refrigerant which has been supplied through distributors III, t8, I29, 20, in substantially equal amounts to the passes of the evaporator, will be vaporized to a. greater extent. in pass 13- than in pass I 6 when the .refrigerant has traversed or flowed through the lower half of the said passes; and the. provision of cross-over 2.5v which connects pass It with pass I3 will'supp'ly an addedamountv ofliquid refrigerant to the upper half of pass I3 to .-assist in. meeting the: requirements of the. heavy :heat

loadimposed. upon'the; said pass by theair current. For the-samereason, but. withz a converse application, pass I 3 is formedwithza cross-over :25! which connects-it withpass. t6: so; that; the upper. portion. of the .latter pass will. be supplied with an increased amount. of, vaporized; :reftig erant. in; .consonance with the relatively :lig-lrt-rheat load imposed uponit. Similarly, pass. I5 is .formed; with. a cross-over 12.8 connecting it with pass 14 to increase.- the supply liquid refrigeerant in the upper half of the lattemxwhile pass 44 has a cross-over 2:9: connecting it withzpass -;I-5- to increase .the ..s.upp y of vaporized r fri ran in thepupper' half of; the: latter.-

(crisscrossing of; the branch; connections of. the evaporator passes sshownwand described asposi- :tioned substantially at the middle of the evaporator, it could be positioned nearer the inlet or nearer tl'iei outlet .of the evaporator passes; in accordance with engineering desires or require- :ments andy'or in accordance with the needs of particular installations; and, furthermore, part of the cross-over connections could be nearer the evaporator inletxand' part "nearer the evaporator outlet; or, finally; only some of the evaporator passes, instead of all, couldbe connected with another-or others. Thus, by way of illustration andwithout limitation, cross-overs 28' and 29 could be omitted; orcross-oversZS and '21 could be omitted; or pass I3 could be cross connected with pass I4 or 1-5,, and pass 16' could be .cross connected with pass I4 or I; since the principle of this feature of. the "invention involves recognition of the. inequality in heat load imposed upon the several passes of the evaporator as they are spaced. further and further: from the side thereof towards which the air current flowsand makes, provision; for; equalizing, atfl'eas't in. large part, the functioning .of the individual. passes and, increasing the.v efiiciency of the evaporator as a whole by causing the passes having the lighter heat load to share a portion of their unused liquid refrigerant with the passes having the greater heat load, so that the output of refrigerant from each evaporator pass into the outlet manifold 25 will be comparable and substantially alike in respect to relative percentage of liquid and gaseous refrigerant and also with respect to temperature, such as the slight superheat hereinabove mentioned.

In connection with the immediately foregoing description, it seems desirable to explain that, as is plainly evident from the drawings, the conduit marked I3 in fact has its inlet at the bottom left hand side of the main evaporator, as viewed in Figs. 1, 2 and 4, and its outlet at the upper right hand side; while the conduit marked 16 has its inlet at the lower right hand side of the main evaporator and its outlet at the upper left hand side; the two said conduits being crossed intermediate their inlets and outlets. The samefact is true with respect to the conduits marked it and I5. Hence, the foregoing description relating to the cries-crossing of the conduits or passes of the main evaporator could have recited that the lower portion of the conduit I 3 is nearest the side of the evaporator toward which the air current moves while its upper portion is furthest therefrom; and that the lower portion of conduit I6 is furthest from the said side of the evaporator while its upper portion is nearest thereto. Corresponding language could also have been used with respect to conduits I 4 and [5. However, inasmuch as the conduits or passes of evaporators are commonly arranged in spaced vertical planes side by side, it has seemed easier to consider and mark the several conduits as in such a side by side, sequential arrangement, and to describe their intermediate portions as cries-cross connected, since the functioning is the same regardless of whether one form of description or the other be adopted. r

The outlet manifold 25 of the main evaporator 1 is connected by a conduit til, which may be an integral part of the said manifold or couerably sinuous in form, but is relatively large in cross section because it receives the output from all four passes of the main evaporator. The auxiliary evaporator 3| is positioned intermediate the fan H and the main evaporator I and it is shown as substantially one-half the height of the main evaporator, although its di mension in this respect, as well as the size and number of its pass or passes, can be varied as occasion may dictate. The inlet of the auxiliary evaporator is preferably at the lower part thereof, as indicated by 33, and its outlet at the upper part thereof, as indicated at 34; the said outlet being connected by the suction'conduit or line 8 with the inlet of the compressor I.

The function of the auxiliary or after evaporator 3| is to evaporate that portion of. the refrigerant emitted from the passes of the main evaporator which has remained in liquid form;

which function not only serves to increase the refrigerating effect of the system, but also insures that the refrigerant flowing back to the compressor will be entirely, or at least approximately entirely, in gaseous rather than liquid form, thus facilitating the operation of the compressor and avoiding possible injury thereto arising from the slugging of liquid'refrigerant through its suction port. This elimination of liquid refrigerant from the suction line also prevents it from so affecting the feeler bulb IO' as to cause the latter to throttle the expansion valve 5 with the result of diminishing the supply of refrigerant to, and so to speak, starving the main evaporator. The location of the auxiliary evaporator intermediate the fan and the main evaporator causes it to receive a heavier heat load from the air current than is received by any of the passes of the main evaporator, which fact enhances the evaporating effect of the auxiliary evaporator upon the refrigerant passing therethrough and thus improves its functional effects just mentioned, as well as permitting it to be of comparatively small size.

In the operation of this form of the invention represented in Fig. 1 of the drawings which has been hereinabove described, the refrigerant compressed by the compressor and condensed by the condenser travels from the latter, or from a receiver associated therewith, tov the expansion valve, and from it to the main evaporator I in a manner well understood by those in this industrial field. The refrigerant flows through the passes of the main evaporator, that may be criss-cross connected, as previously described; thence to the outlet manifold 25, through conduit 38, through pass 32 of the auxiliary evaporator 3i, and finally through suction conduit or line 8 back to the compressor I. The construction and arrangement of the invention is such that, as already indicated in the description thereof, all the passes of the main evaporator 1 function with a high degree of efficiency, each pass being fully wetted with liquid refrigerant, while the refrigerant flowing from the main evaporator through auxiliary evaporator 3| causes the latter to increase the refrigcrating effect of the system and to insure that the refrigerant flowing back to the compressor has been entirely or approximately entirely exhausted with respect to its refrigerating value and is in proper condition to be received and recompressed by the compressor.

The modified form of the invention represented in Fig. 2 of the drawings is the same in construction, arrangement and mode of operation as that shown in Fig. 1, except that the refrigerant supply conduit or line 4 leading from the condenser, or condenser and receiver, 3, to expansion valve 5, has a part thereof marked 35 in juxtaposition and heat exchange relation with a portion of the suction conduit or line 8. Thi serves to elevate the temperature of the said portion of the line a, because the refrigerant in line 4 is warm, and thereby further to insure the complete evaporation of the refrigerant flowing back to the compressor in case by any chance the auxiliary or after evaporator 31 has failed completely to evaporate or gasify all the liquid refrigerant passing therethrough. The shape of the suction line 8 and of the expansion valve control tube 9 in this modified form of the invention shown in 2 diners somewhat from the shape shown in Fig. l, but this difference is for engineering or installation purposes and is not functional except that the U-shaped part of the suction line 8 provides a convenientlplace for positioning the feeler bulb Hi intermediate the auxiliary evaporator 3i and the zone 35 in which thfiSuPDlYfllnEfl and suction. linetflxare i n heat exehangemel'ation.

Fig1fi3, as noted in the description of. thefigures of the drawings atthe outset-of this specification, shows a vertical section taken :irrthe plane of the line III-J11 of Fig.1; and it illustrates the general appearance and arrangement of the parts of the mainevaporator i and zauxiiliary evaporator 31 when viewed at right angles to the representationof these parts in Figs. 1 and 2'.v This Fig. 3 also shows the fin plates. on the auxiliary evaporator which are denoted by 3| becauseit is to such a fin plate that the leader line from the numeral 3! in Figs. "1' and .2 runs whendesignatin the auxiliary evaporator as a whole; Similar fin plates are also-providedv on the main evaporator" as also shown in Fig. 3; If desired, the same fin plates could be used for both the main and auxiliary evaporators, i. e., an integral construction.

I -lg. 4. shows a'second modified form of the invention in which the auxiliary or after evaporator is embodied within the main evaporator, all other parts or" the system being the same as illustrated in either Fig. 1' orFig. 4, the auxiliary evaporator conduit or pass, here marked 35', is positioned intermediate passes M and 1-5- of the main evaporator, and pass '36 is somewhat greater in length then in the forms of'F-igs. "1 and 2, which increase in length is indicated by its greater height in Fig. 4. The said pass '36 is-connected at the center of the outlet manifold, here marked 3'1, of the main evaporator, as 'indicatedat 38, and its other end communicat'es through a conduit 39 with the suction line &3. The greater length of'the auxiliary evaporator in the form of Fig. i is called for mainly by the fact that it is not interposedbetween the main evaporator and the incoming air current so'as to receive the greatest heat load as" is the case with the forms of the invention shown in Figs. 1 and 2. Consequently, the evaporating effect of the auxiliary "or after evaporator of Fig. l is, per unit of size and other factors being equal, less than in the case of the arrangement of Figs. 1 and 2. On theother hand, the form of Fig. l has advantages because of its compactness and unitary character which are important in connection with transportation and installation. The auxiliary evaporator pass 38 of Fig; l is notprovided with its own fins, but shares the fin plates of the main evaporator.

' Asthe mode of operation of the formof inventlon shownin Fig. 4 is like that of thezother forms, th'eifeiis deemed to be no occasion here to repeat the same other than to note, as alreadypointed out,..tha't th'e'pass of the auxiliary evaporator receives the refrigerant from a point intermediate the ends of the outlet manifold 37 rather than from one end thereof, and that'it is nested within the conduits or passes of the main evaporator so that itdOes not directly receive the impingement of the air stream prior to the entry thereof into thevlatter.

Withv respect to all forms of the invention, it should. be stated that the criss-crossed interconnection of the conduits or passes of the main evaporator is not a necessary feature, because the auxiliary or after evaporator .can perform its function even though the effects of the individual passes of the main evaporator are not brought towards equalization by the fact of their criss-crossed interconnection. Indeed, it is practical deliberately to supply an excess of liquid refrigerant to the main evaporator so that the In this Fig.

8 passesthereotnearerito the side-of theievaporator towardsrwhich the air currentz'flows..-may beassured of. having an adequate amount of liquid :refrigerant to perform at peak efliciency, even though this .causesan excess of liquid to be emitted from the passes more distant from the-.said side of the evaporator, because the auxiliary or after evaporator will vaporize. this excess. But the criss-cross arrangement permits reductionin thesize or the auxiliary evaporator.

It will be understood that various changes may be resorted to in the form, construction and arrangement of the parts without departingtrom the spirit or scope of the invention, and hencel do not intend to be limited to details Jherein shown or described except as they may beincluded in the claims or be required by disclosure of the prior art.

What I claim is:

1. An evaporator assembly designed and adapted to cool a single air stream in heat "exchange systems comprisingua main evaporator having a plurality of conduits provided with refrigerant inlets and outlets, an auxiliary after evaporator having an inlet connected with the outlets of the main evaporator conduits, and means for generating an air stream, the parts being so constructed and arranged that the after evaporator is adapted to augment the cooling chest of the main evaporator on the air stream and itself to evaporate the liquid portion of refrigerant supplied to the main evaporator which is not evaporated during its passage through "said main evaporator, the said auxiliary after evaporator including a conduit of relatively large cross sectional size as compared with the conduits of the main evaporator to adapt the auxiliary after evaporator to receive the combined output of all conduits oi the main evaporator, and the means for generating an air stream beingarranged 'to force the air stream directly through the auxiliary after evaporator and the main evaporator.

2. An evaporator assembly designed and adapted to cool a single air stream in heat exchange systems comprising, a main evaporator having a plurality of conduits provided with refrigerant inlets and outlets, an auxiliary after evaporator having an inlet connected with the outlets of the main evaporator conduits, and means for generating an air stream, the parts being soconstructed and arranged that. the aiter evaporator is adapted to augment the cooling efiect of the main evaporator on the air stream and itself to evaporate the liquid portion of. nefrigerant supplied to the main evaporator which is not evaporated during its passage through said main evaporator, the conduits of the saidv main evaporator .being arranged in substantially parallel relationship and at least oneof. said conduits located further from thesideof the main evaporator toward which the air current moves being connected by a refrigerant conducting cross-over with at least one other conduit located nearer the said side of the main evaporator, the points of connection. being, between the-inlets and outlets of said conduits connected by the cross-oven 3. An evaporator assembly as defined in. claim 2, which also includesindividual refrigerant .distributors connected with the inlets of the main evaporator. conduits.

4. An evaporator assembly as defined in claim 3, which also includes .an outlet manifold interconnecting the outlets. of. the main evaporator conduits and the inlet of theauxiliary after evaporater.

5. An evaporator assembly designed and adapted to cool a single air stream in heat exchange systems comprising, a main evaporator having a plurality of conduits provided with refrigerant inlets and outlets, an auxiliary after evaporator having an inlet connected with the outlets .of the main evaporator conduits, and means for generating an air stream, the parts heing so constructed and arranged that the after evaporator is adapted to augment the cooling effect of the main evaporator on the air stream and itself to evaporate the liquid portion of refrigerant supplied to the main evaporator which is not evaporated during its passage through said main evaporator, the said auxiliary after evaporator being positioned between two of the main evaporator conduits.

6. An evaporator assembly as defined in claim 5, which also includes a manifold for the outlets of the main evaporator conduits to which manitold the inlet of the said auxiliary after evaporator is connected at a point within the main evapo- 

